In systems, such as radiation therapy systems, ionizing radiation techniques are used to treat various tissues, such as tumors. At least some known ionizing radiation techniques that are used in radiation therapy systems include electron beams, x-rays, and proton beams. These techniques enable a radiologist to treat patients from multiple angles, while also varying the shape and dose of the radiation beam. This approach also enables the delivery of radiation to a target within a treatment volume while avoiding excess irradiation of adjacent healthy tissue. In order to deliver radiation appropriately, treatment planning is used.
At least some known treatment planning methods consider various parameters, such as dosage of radiation being delivered, patient setup uncertainty, proton beam range parameters, and/or organ motion. For example, in photon treatment planning, at least some of these parameters are addressed by using geometrical concepts, such as planning target volume (“PTV”). In at least some know methods, the PTV is generated by including geometric margins to the clinical target volume (“CTV”). The CTV to PTV margins can be ascertained by considering uncertainties that can occur during the delivery of the treatment beam.
In proton planning, however, at least some known PTV designs are not able to provide a robust plan. This problem can occur more often for proton planning than photon planning, as protons deposit energy in a different way than photons. As such, patient setup error and internal target motion may have a significant impact on the coverage of a target structure, such as the tissue of a tumor, and the exposure of normal tissue. Moreover, the distal fall of the dose can be relatively sharp or steep. As such, there can be range uncertainty caused by, for example, calibration inaccuracies in the equipment used, such as a computerized tomography (“CT”) scanner. All of these known issues may result in the treatment of more normal tissue that surrounds the target structure (i.e., tumor). Moreover, at least part of the target structure may not get treated. As a result, the target may be unable to obtain the full treatment dose,